The last twenty (20) years have witnessed numerous developments in the use of sinuous springs to replace coil springs. Crosby et al U.S. Pat. Nos. 3,388,904 and 3,525,524 disclose sinuous spring band assemblies which were developed to provide much of the comfort associated with coil spring seating while reducing spring assembly costs dramatically.
Efforts to achieve more sophisticated and improved results with sinuous spring bands have abounded. Morley Furniture Spring Corporation, assignee of the present application and also of the aforementioned patents, has been a leader in this work.
One thing that has eluded Morley and others working in this field is a spring band assembly which precisely proportions pre-compression force along its length, i.e., from back rail to front rail, while providing softness at both front and back rails. Another elusive target has been a seat spring assembly, employing sinuous spring band assemblies, which need employ as few as four band assemblies in a conventional size chair and five band assemblies in a conventional size "wedge" unit.